Abstract
Herein we determine for the first time the reproduction parameters and population structure of Hypostomus francisci in the Itapecerica River, São Francisco Basin. A total of 250 specimens was captured quarterly between March 2010 and February 2012. Body weight, total length and weight of the gonads were obtained in the laboratory. Gonad samples were submitted to histological and histochemical techniques. Females with spawning capable ovaries were used to determine the fecundity and relative fecundity. Sex ratio with 1:1.01 (female:male) was observed. Males were more numerous than females for individuals smaller than 170 mm, however the number of females was significantly greater for specimens larger than 330 mm. The length-weight relationship estimated for H. francisci indicates negative-allometric growth. Females spawning capable were observed mostly in November-December-January. Two cohorts of oocytes at a determined time evidencing the development type group-synchronic. The eggs reaching 3.4 mm and the fecundity ranged from 312-1,460 oocytes with an average of 585.81 ± 337.43 oocytes per female. The reproductive parameters and population structure of H. francisci from Itapecerica River suggested that this species showed singular reproductive tactics among congeners.
Highlights
Quantitative aspects of the population structure and reproductive biology, such as sex ratio, lengthweight relationship, reproductive strategies andAn Acad Bras Cienc (2016) 88 (3 Suppl.)The loricariids exhibit a great variety of reproductive strategies and tactics related to the environment (Suzuki et al 2000)
The length-weight relationship (LWR) was estimated for H. francisci: parameter “b” was 2.883, and parameter “a” was 0.015 with a determination coefficient (R2) equal to 0.94 (p < 0.001) (Fig. 2)
This observation can be related to the fecundity, since larger fish produce more eggs increasing the population number (Murua and Saborydo-Rey 2003). It was observed a high correlation between fecundity and total length in H. francisci as well as, with gonadal weight and body weight
Summary
Quantitative aspects of the population structure and reproductive biology, such as sex ratio, lengthweight relationship, reproductive strategies andAn Acad Bras Cienc (2016) 88 (3 Suppl.)The loricariids exhibit a great variety of reproductive strategies and tactics related to the environment (Suzuki et al 2000). The genus Hypostomus Lacépède is the largest genus within the family Loricariidae, with approximately 130 species recognized (Zawadzki et al 2010) This genus habits clear running water on the rocky-bottom of South American Rivers (Garavello and Garavello 2004), as well as, muddy water with soft bottoms and can withstand the barrage events by adapting to reservoirs (Duarte et al 2011). Due to their iliophagous feeding habits, they play an important role in accelerating the recycling of nutrients. There is generalized pollution from organic and industrial effluents from poorly planned municipal sewage systems, which is probably the cause of the primary water quality problems, as indicated by chemical oxygen demand range 2.95 and 7.78 mgL-1 and total coliforms between 10,500 and 56,600 CFU-100mL (Menezes and Faria 2003)
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